1. Technical Field
The present invention relates to a bubble control unit used in a liquid ejecting head for ejecting liquid from a nozzle such as an ink jet type recording head, a liquid ejecting head, and a liquid ejecting apparatus having the same.
2. Related Art
Liquid ejecting heads that discharge (eject) droplets from nozzle s by producing pressure fluctuations in liquid within a pressure chamber include, for example, an ink jet type recording head (hereinafter, simply referred to as a recording head) used in an image recording apparatus such as an ink jet type recording apparatus (hereinafter, simply referred to as a printer), a color material ejecting head used for manufacturing of a color filter such as a liquid crystal display, an organic EL (Electro Luminescence) display, an electrode material ejecting head used for electrode formation of an FED (Surface-Emitting Display) and the like, and a bio-organism ejecting head used for manufacturing of a biochip (biotip), and the like.
For example, in the above-mentioned recording head, an ink introducing needle having an acute angled tip is inserted into an ink cartridge (hereinafter, simply referred to as a cartridge) in which ink in the form of liquid is sealed, so that ink within the cartridge is introduced into a pressure chamber of the recording head through an introducing hole set up in the tip of the ink introducing needle.
In the recording head according to the above-mentioned configuration, ideally, an ink channel extending from the ink introducing needle to the nozzle of the recording head is filled with ink. However, bubbles may intrude into the ink channel during the filling up (initial filling up) of ink within the recording head or the replacement of the ink cartridge and the like. For this reason, it is difficult to completely prevent the bubbles from being mixed in. If the bubbles intruding into the ink channel gradually grow to become larger, and a portion of the bubbles grown to an excessive size moves toward the pressure chamber due to the flow of ink, it may cause drawbacks of pressure loss due to absorption of the pressure fluctuation in operation of discharge by the bubbles, or shortage in supply of ink due to clogging of the channel by the bubbles, and the like.
In order to prevent the drawbacks caused by such bubbles, a recording head where the filter is mounted in the ink channel between the ink introducing needle and the head body has been proposed (see, for example, JP-A-2007-136687). This recording head is configured to be provided with grooves on an inner surface of the ink introducing needle, and to be capable of preventing the ink channel from being clogged up by the bubbles accumulated within the ink introducing needle.
However, in the above-mentioned recording head, since the filter is disposed parallel to the nozzle surface on which the nozzle is formed, and recent recording heads have been downsized, it has been difficult to augment the space for gathering the bubbles within the ink introducing needle, or to enlarge an area of the filter. For this reason, it has been necessary to frequently perform a cleaning operation for discharging the bubbles.